We propose to utilize polymer and physical chemistry and cariology to develop and test novel synthetic resins for blocking dental caries initiation and/or promoting tooth remineralization. These resins will be capable of ion-exchange release of fluoride ions into the immediate vicinity of tooth surfaces. Our previous results have shown that acrylic fluoride-ion exchanging resins are promising materials for treatment of incipient carious lesions and that the properties of such resins can be adapted to the requirements of preventive, restorative and prosthetic dentistry. Thus such resins have potential for use as fissure sealants, adhesives, bonding agents, composite restoratives, bite splints and related applications where extended fluoride release would be of benefit. Therefore the major objective of the proposed research will be to develop a family of fluoride-exchanging resins having varying rates of release and physical, chemical and biological safety characteristics that are satisfactory for extended use in the mouth. Specifically, we propose to: 1. Formulate fluoride-exchanging acrylic dental resins. 2. Evaluate properties related to dental material requirements: setting time, initial mix viscosity, initial set hardness, moisture uptake, solubility, marginal leakage, and retention of hardness and adhesion in water. 3. Determine fluoride-release rate into solution and fluoride-uptake into enamel, in vitro. 4. Evaluate the caries-inhibiting potential of promising resins, in vitro, using acid gel demineralization and polarized light microscopy. 5. Evaluate the biological safety, in vitro, using the Ames mutagenicity assey and tissue culture quantitative cytotoxicity.